Extension advice: Do not exhibit lactating dairy cows at public events through 2024

This article has specific recommendations for animal exhibitions in 2024 in Minnesota due to the outbreak of H5N1 in dairy and poultry operations across the state and country. It also contains information about the spread of influenza A viruses relevant to the general public and people involved in farm animal operations.

Given the high risk posed by lactating dairy cattle to other cattle, the rest of the exhibition community, and the public, lactating dairy cattle should not attend exhibitions including county and state fairs, until 2025 or beyond.

H5 influenza background

On March 25, 2024, USDA APHIS confirmed the detection of H5N1 in dairy cattle in Texas and Kansas. Since March 25, 2024, detections of H5N1 influenza in dairy cattle have been reported in many herds throughout the United States. H5N1 historically infects birds but it also infects many types of mammals including humans, cats, dogs, raccoons, bears, skunks, and foxes. (For a list of infected species see 2022–2024 Detections of Highly Pathogenic Avian Influenza (usda.gov).

Cattle infected with H5N1 virus have typically recovered and current virus strains have caused very few cow deaths. In affected dairy herds, approximately 10 to 20 percent of cattle are clinically sick, with most cases being mid to late-lactation mature cows.

In contrast to the disease in cattle, infections from the same virus (H5N1 clade 2.3.4.4b strain B3.13 influenza A virus) in other species, like chickens, turkeys, and cats, have been deadly. In addition to causing high mortality in poultry flocks, there is mandatory depopulation and disposal of all birds on H5N1-positive premises. This has substantial economic and emotional impacts on the farmer and the industry.

Transmission

Raw milk has the most infectious H5N1 influenza virus. Dairy cattle testing has shown high viral loads in raw milk from infected cows. However, other samples from cattle including nasal swabs, lung tissue, and urine have also tested positive meaning they may also play a role in viral transmission.

As of this writing, the exact way that the H5 influenza virus spreads between dairy farms and from dairy farms to poultry farms is not fully understood. However, several studies have looked into possible risk factors associated with infected farms. Key potential links between infected dairy farms (both dairy to dairy and dairy to poultry) include sharing equipment, personnel, visitors, movements of animals, and the presence of other wild or domestic animals on the premises.

It's important to highlight a USDA epidemiological study involving dairy and poultry farms in Michigan. Out of 15 infected dairy farms studied, only 6 had received new animals within 30 days of detecting the H5 influenza virus. This suggests that the virus is spreading between farms through mechanisms beyond just the movement of cattle. These identified links between infected farms often involve local geographic connections, meaning the infected farms are located relatively close to each other.

Human infections with H5 influenza virus

Several human cases of H5 influenza have been officially reported in 2024 and are associated with direct contact with either infected dairy cattle or poultry. At the time of this publication, these cases have been mild with conjunctivitis, respiratory signs, fever, chills, and sore throat reported by the CDC. At the time of this publication, all of the people reported to have an H5 influenza virus infection have fully recovered.

While cases have been mild, so far, influenza researchers have identified factors that may allow the virus to become even more infectious in mammals and perhaps change enough to cause human-to-human transmission.

H5 influenza virus can change

Influenza A viruses change over time as they spread. These changes happen when the virus mutates or interacts with other influenza A viruses. These changes can affect how deadly and contagious the virus is. When the H5 influenza virus spreads more widely, it gets more chances to develop traits that could make it more dangerous or easily spread to different species, including humans.

To prevent the risk of outbreaks spreading to new animal groups and humans, it's important to minimize opportunities for the H5 influenza virus to spread and interact with other viruses. Events like shows, fairs, and exhibitions where different animals and people gather, and where influenza A viruses are present, have led to infections in new hosts and the emergence of new virus types.

What is the risk?

A risk assessment for H5 influenza virus has two main parts: first, how likely it is to be exposed to the virus, and second, what happens if that exposure occurs. These parts work together to determine the overall risk.

To evaluate the risk of H5 influenza in a specific situation, we need to consider both factors. If the chance of exposure is low but the consequences of exposure are serious or very serious, then the overall risk is likely high.

Currently, there are only a few known cases of H5-infected dairy farms in the state, so the likelihood of exposure might be low. However, the consequences of having an infected dairy cow at a fair are significant. Therefore, bringing lactating dairy cows to shows, exhibitions, or fairs carries a high overall risk.

Based on past experiences with infectious diseases and understanding of animal exhibitions, the consequences of H5 influenza in animals at such events include:

• Cattle could become infected and potentially spread the virus when they return home after the fair.
• Exposure of other species, including humans.
• The spread of infection within these species could lead to severe outcomes like the death of poultry.

These outcomes could have serious effects on dairy herds, poultry flocks, public health, and the reputation of fairs and exhibitions. The outcomes would also result in increasing the virus's circulation, potentially leading to further changes to the virus.

The risk of H5 influenza virus infecting dairy cattle and causing an outbreak at exhibitions is considered high. Although cattle are tested before exhibitions to reduce the risk of bringing in an infected cow, a single test cannot guarantee the cow will remain virus-free.

The exposure risk for H5 influenza in dairy cattle varies because the prevalence of the virus across the state is unclear. However, the expected consequences of introducing and spreading H5 influenza at fairs are severe.

When we weigh these factors together, the overall risk associated with bringing lactating dairy cattle to exhibitions is high.

Recommendations for exhibitions, including county fairs and state fairs

The authors of this article advise that lactating dairy cattle not attend exhibitions through the end of 2024, regardless of premovement testing requirements, based on the following information about H5 influenza in dairy cattle:

• The virus successfully infects lactating dairy cows and is concentrated in milk.
• The risk of exposure to H5 influenza for both animals and humans at fairs and exhibitions is high.

At the end of the 2024 fair season, we also recommend a policy review, with revision and extension appropriate to the evolving situation.

Milking

Raw milk is known to be the most infectious material associated with H5 influenza in dairy cattle and poses a risk to humans, cattle, poultry, other livestock, cats, and other pets. H5 influenza virus in raw milk from infected dairy cows is present in such high numbers that a single infected cow at an exhibition could effectively spread the virus to many (or all) other attending species and humans. This is especially true given that lactating dairy cattle must be milked while attending an exhibition.

Milking is often done in a shared parlor and may involve shared equipment, which is an efficient way to spread H5 influenza. Although closing the parlor seems like a logical control step, that strategy will simply spread the virus source since the lactating cow must still be milked, which is now likely to be done in the cow’s stall, and the milk must still be stored and marketed or discarded.

Keep lactating cows home

Overall, the risk of H5 influenza in fairs and exhibitions in Minnesota is high. Fortunately, these risks can be mitigated by lactating dairy cows not attending fairs and exhibitions in Minnesota in 2024.

While some may see the spread of H5 influenza as unlikely to happen, the potential consequences could be severe. Removing lactating cows from the equation could effectively eliminate most, if not all, of the risk of exposure.

This article shares what is currently known about H5 influenza in the context of exhibitions. Ultimately, the decision on which policies to adopt lies with those managing risks (such as exhibition organizers or regulators), considering the social and community context. We hope our summary of the risks in this scenario will help inform these decisions.